Ink jet printers of the prior art include a printhead having ink ejecting nozzles therein, the printhead being pulled back and forth across a record path as ink is intermittently ejected from the nozzles to place small dots of ink on a record sheet. The dots overlap so as to create characters or graphic images. Recent developments have enabled printing with dot densities of up to 600 dots per inch. Obviously, accuracy of dot placement is of utmost importance if characters and lines are to be printed without ragged or uneven edges.
It has been conventional to mount an ink jet printhead on a carrier which is slidable on a guide rod extending transverse to the record feed path. A belt, driven by a bi-directional motor, is attached to the carrier such that the printhead carrier is pulled in a first or a second direction on the guide rod depending on the direction of rotation of the motor. In the prior art it has been the practice to attach the belt to the carrier at a single point or at aligned points on opposite sides of the carrier. That is, a straight line drawn between the points of attachment of the belt is parallel to the axis of the guide rod. This arrangement leads to variations in dot placement depending upon the direction in which the printhead carrier is being pulled at the time ink is ejected from a nozzle. This variation in dot placement results from the fact that a small clearance must be provided between the printhead carrier and the guide rod upon which it slides in order to permit free sliding movement. Because of wear, this clearance increases with printer use. The clearance enables the carrier to "tilt" on the guide rod in either a first or a second direction depending upon the direction in which the carrier is being pulled by the belt. The tilting moves the ink jet nozzles in an arc so that ink is no longer ejected from the nozzles in a direction normal to the record. Ink dots are thus displaced from the ideal print position by a distance d.sub.1 or d.sub.2, these distances extending in opposite directions from the ideal print position.